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1、苏州大学本科毕业设计(论文)Based on AT89C52 LED overviewLED (Light Emitting Diode), light-emitting diode, is a solid state semiconductor devices, which can be directly converted into electricity to light. LED is the heart of a semiconductor chip, the chip is attached to one end of a stent, is the negative side,
2、the other end of the power of the cathode, the entire chip package to be epoxy resin. Semiconductor chip is composed of two parts, part of the P-type semiconductor, it inside the hole-dominated, the other side is the N-type semiconductor, here is mainly electronic. But linking the two semiconductors
3、, among them the formation of a PN junction. When the current through the wires role in this chip, will be pushing e-P, P zone in the hole with electronic composite, and then to be issued in the form of photon energy, and this is the principle of LED luminescence. The wavelength of light that is the
4、 color of light, is formed by the PN junction of the decisions of the material. LED history 50 years ago, people have to understand semiconductor materials can produce light of the basic knowledge, the first commercial diodes in 1960. English is the LED light emitting diode (LED) acronym, and its ba
5、sic structure is an electroluminescent semiconductor materials, placed in a wire rack, then sealed with epoxy resin around, that is, solid package, Therefore, the protection of the internal batteries can play the role of line, so the seismic performance LED good. LED is the core of the P-type semico
6、nductor and components of the N-type semiconductor chips, the P-type semiconductor and N-type semiconductor between a transition layer, called the PN junction. In some semiconductor materials in the PN junction, the injection of a small number of carrier-carrier and the majority of the extra time wi
7、ll be in the form of light energy to release, thus the power to direct conversion of solar energy. PN junction on reverse voltage, a few hard-carrier injection, it is not luminous. This use of injection electroluminescent diodes is produced by the principle of light-emitting diodes, commonly known a
8、s LED. When it in a positive state of the work (that is, at both ends with forward voltage), the current flows from the LED anode, cathode, semiconductor crystals on the issue from the ultraviolet to infrared light of different colors, light and the strength of the currents. Instruments used for the
9、 first LED light source instructions, but all kinds of light colored LED lights in traffic and large screen has been widely applied, have a very good economic and social benefits. The 12-inch red traffic lights as an example, is used in the United States have long life, low-efficiency 140 watt incan
10、descent lamp as a light source, it produced 2,000 lumens of white light. The red filter, the loss-90 percent, only 200 lumens of red light. In the light of the new design, Lumileds companies have 18 red LED light source, including the loss of circuit, a total power consumption of 14 watts to generat
11、e the same optical effect. Automotive LED lights is also the source of important areas.For general lighting, people need more white light sources. The 1998 white LED successful development. This is the GaN LED chip and Yttrium Aluminum Garnet (YAG) package together cause. GaN chip of the Blu-ray ( p
12、 = 465nm, Wd = 30nm), made of high-temperature sintering of the Ce3 + YAG phosphors excited by this Blu-ray after irradiating a yellow, the peak 550 nm. Blue-chip installed in the LED-based Wanxing reflection in the cavity, covered with a resin mixed with YAG thin layer, about 200-500 nm. LED-based
13、tablets issued by the Blu-ray absorption part of the phosphor, the phosphor another part of the Blu-ray and a yellow light mixed, can be a white. Now, the InGaN / YAG white LED, YAG phosphor by changing the chemical composition of the phosphor layer and adjust the thickness of the 3500-10000 K color
14、 temperature can be colored white. This blue LED through the method by white, constructed simple, low-cost, high technology is mature, so use the most. In the 1960s, the use of science and technology workers semiconductor PN junction of The principle of developing a LED light-emitting diodes. At tha
15、t time, the development of LED, the materials used are GaASP, its luminous color is red. After nearly 30 years of development, and now we are very familiar with the LED, has been sent to red, orange, yellow, green, blue, and other shade. However lighting necessary for white LED light only in recent
16、years to develop, readers here to tell us about lighting with white LED.The LED display screen and video display into the text by LED matrix blocks. Graphic display can be displayed with computer, English, Chinese text and graphics, Video screen using microcomputer control, graphic, image, with real-time, synchronization, clear information dissemination way play all kinds of information, but also shows 2d, 3d animation, videos, TV, VCD programs and live. The LED disp
